1. Field of the Invention
The present invention is in the field of medical equipment and specifically relates to a lightweight splint for use on a human elbow or knee for accomplishing a progressive extension of the limb to which it is applied.
2. The Prior Art
The present invention employs a composite body material consisting of an aluminum endo-skeleton molded into a matrix of closed cell polyethylene foam.
The attractiveness of this type of composite material was first recognized in U.S. Pat. No. 3,942,522 issued Mar. 9, 1976 to Kinnier Wilson. The polyethylene cushions the aluminum mesh used and protects the patient from any sharp edges or burrs.
The use of aluminum wires embedded in a polyethylene foam matrix is shown in U.S. Pat. No. 4,928,677 issued May 29, 1990 to Barber and in U.S. Pat. No. 5,058,576 issued Oct. 22, 1991 to Grim, et al.
This composite body material has a number of properties that make it particularly attractive for use in orthoses. It is light in weight, odorless, and does not absorb moisture. Consequently, it does not encourage the growth of bacteria and is easily cleaned with soap and water or alcohol. The aluminum wires or mesh provide a degree of stiffness which is adequate to maintain its shape against casual applied forces, but which is readily deformed by the deliberate application of stronger forces. This permits the orthosis to be supplied in a flat condition and then to be shaped by a skilled practitioner to accommodate the particular shape and size of the patient's limb. Once shaped in this manner, the orthosis has no tendency to revert to its original shape, thereby permitting the splint to "lock in" or retain the degree of extension imparted by the care giver.
The present invention employs this type of composite material to advantage, but the material itself is not the present invention.
Many patients, upon reaching an advanced age, show a tendency for their arms or legs to assume a permanent retraction, i.e., the elbows and knees flex to a contracted position.
When properly used, the orthosis of the present invention can reverse this condition, at least partially, when used in the following manner. A skilled therapist exercises the affected limb by moving it through its entire range of motion and by gently applying an extending force to the limb. Immediately after such exercise, the orthosis of the present invention is applied to hold the limb in the most extended position achieved that day. The same procedure is followed in successive sessions, and the extension gained in each session is maintained by the orthosis. In this way, over a number of days, the orthosis accomplishes a progressive extension of the limb.
As can be appreciated, under such a program of exercise it is not unusual for the limb to spasm, which might cause the patient to retract his limb with sufficient force to alter the shape of the orthosis.
The tendency to spasm is a possible negative effect of this otherwise highly beneficial technique of progressive extension.
Confronted with this potential limitation on the use of the progressive extension technique, the present inventor set out to find a way to counteract the negative effect of spasms.